1. Technical Field
This invention relates to the art of making stamped metal articles and, particularly, to the art of making stamped metal articles for use as rockers arms in internal combustion engines.
2. Description of the Prior Art
Low carbon stamped or cast steel rocker arms have been used heretofore. However, the sequence for forming such rocker arms has consistently included forming a channel of such metal to provide a strong structure which can withstand the forces to which such rocker arms are subjected, followed by shaping operations and chemical treatments. Shaping operations have included drilling, reaming, and threading; chemical treatments may include thermal baths, cyaniding and sulfur treatments. Joining of composite members or plys of the formed channel, such as by welding (see U.S. Pat. Nos. 3,418,985; 4,430,783), is also performed subsequent to channel formation. Such joining of laminated plys of the assembly may be by clamping and upsetting.
The problem associated with the above method steps is cost, which is held at a relatively high level because the life of the tools used to perform the shaping operation is low, the apparatus and sequential steps required for chemical treatment are expensive, and the extra steps required for the joining of plys or composites is added expense. But, most importantly, by employing a variety of shaping steps subsequent to the formation of the arm channel inhibits the speed of making the completed rocker arm and prevents such techniques from fitting well with "just in time" inventory techniques so prevalent in the emerging modern factory. Moreover, finger follower arms, which are a special type of rocker arm, are subjected to operational stresses, which must be considered in the arm design and in the past has limited the method of making. Such arm design must provide for higher strength and hardnesses which qualities, if present in the starting material, inhibits fabrication.